This application claims the priority of German Patent Document 198 10 290.9 filed Mar. 10, 1998 and PCT/EP99/01162 filed Feb. 23, 1999, the disclosures of which is are expressly incorporated by reference herein.
The invention relates to a data bus for a plurality of nodes which are connected to one another via a star coupler. A data bus of this type is known from the German Patent Application 19720401 not previously published. Therein the nodes are connected to the data bus via transmitter/receiver modules. In particular when nodes which issue optical data information are connected to the data bus, a malfunction of the bus node may occur (for example, continuous transmission of information) or there may occur a fault in a transmitter/receiver module (for example, if the output of an opto-electrical transducer used in the transmitter/receiver module remains outside of the signal traffic even at the Low level, which actually occurs only in the case of signal traffic). This malfunction or fault blocks bus communication. In this case the source of the fault cannot be determined automatically and it is also not possible to intervene automatically Therefore, bus communication continues to be disrupted until it is repaired.
The objective of the invention is to provide a data bus which is able to monitor the data traffic on the data bus and in particular to exclude a node from bus communication.
According to the preset invention, a series of individual measures, in combination, are used to obtain the desired effect. On the one hand optical signals case are converted into electrical form and fed as input signals to the star coupler. The star coupler itself contains a logical decision gate to which the input signals are fed and whose output is connected in a parallel manner via an electrical line to the inputs of the nodes. To each input of the decision gate a switch is connected in parallel which can be activated if necessary and which interrupts the transmission segment between the node and the decision gate thereby separating the node from the data bus.
Because the switch is addressed, it is possible in a simple manner to separate only a single node from the data bus.